Water heater



Jan. 27, 1931. T. G. ARRowsMlTH WATER HEATER Filed June 7, 1927 @frzw A TTORNE YS Patented Jan. 27, 1931 UNITED STATES THOMAS G. ARROWSMITH, OF SAN FRANCISCO, CALIFORNIA WATER HEATER Application led .Tune 7,

This invention relates generally to liquid heaters for water supply systems, and is particularly adapted for use with fuels such as natural or artificial gas.

It is an object of this invention to devise a liquid heater which will be efficient and economical in consumption of fuel, and will be dependable in use. r

It is a further object of this invention to devise a liquid heater which will be simple in construction and comparatively cheap to manufacture.

It is a further object of this invention to devise a liquid heater in which the heat exchange means will be so designed as to cause uniform heating of the liquid throughout the tank.

It is a further object of this invention to devise a liquid heater which will not operate to store a layer of heated liquid at the top of the tank during operation, but which will effect positive thermal circulation so that the liquid is heated uniformly at all times.

Further objects of this invention will appear from the following description in which I have set forth the preferred embodiment of my invention. It is to be lunderstood that the appended claims are to be accorded a range of equivalents consistent with the state of the prior art.

Referring to the drawing:

Figure 1 is a transverse cross sectional elevational view illustrating a liquid heater constructed in accordance with this invention.

Fig. 2 is a cross sectional view taken along the line 2-2 of Fig. 1.

This invention makes use of the usual type of liquid Storage tank having its lower portion in communication with a source of cold water, and having a pipe communicating with its upper portion for withdrawing hot water. A gas or other type of fuel burner is utilized for supplying heat, and heat exchange means is provided within the tank for transferring heat from the products of combustion to the liquid. It is the design of this exchange means which forms one of the most important fea-tures of this invention.

Referring to the drawing there is shown a liquid tank 10 of usual construction, vwhich 1927. Serial No. 197,156.

is preferably in upright position. Extending through the upper end of the tank there is a pipe 11 which communicates with a source of cold water, and this pipe terminates adjacent the lower portion of the tank. Connected with the upper tank portion, there is a pipe 12 which supplies a hot water piping system, through which the hot water is withdrawn as desired. The exterior of the tank is preferably covered by a jacket 13 of heat insulating 60 material. Positioned adjacent the lower portion of the tank, there is shown a main gas burner 14 which is preferably operated in conjunction With a suitable pilot burner 16.- Gas is supplied to burner 14 thru pipe 17 and is 65 controlled by means of a suitable automatic thermostat valve 18. The construction of valve 18 need not be described in detail, since such valves are common in the art. It is suliicient to say that this valve is operated in conjunction with a thermostat element 19 which is in thermal contact with the liquid adjacent the point of introduction of the cold Water thru pipe 11.

In'order to transfer the heat supplied by the flame of the burner to the liquid, I have provided suitable heat exchange means which preferably extends substantially the height of tank 10 and is so designed that it causes a positive circulation of liquid within the tank. In constructing this heat exchange means I prefer to employ a heat exchange tube 21 which extends a substantial distance into the tank from the lower portion thereof. For example I have shown such a tube extending vertically through the bottom wall 22 of tank 10. In order to provide effective heat transferring contact between the products of combustion of the burner iiame, and the walls of the heat exchange tube 21, the products of combustion are conveyed'up thru tube 21 thru a passageway and are then caused to move downwardly along the inner walls of the tube. This assageway is preferably in the form of a Ere tube 23 which is substantially smaller in diameter than tube 21. Burners 14 and 16 are arranged to project their :flame into the lower portion of fire tube 23, and the upper end of this tube terminates short of the upper end of heat exchange tube 21. Tube 23 is preferably removable to permit replacement, and for this purpose it has been shown as mounted upon a suitable plate 24 which is detachably secured to the bottom support base 26, as by means ot' bolts 27.

After the products of combustion have been caused to move downwardly along the inner` walls ot' tube 21, they are dischared thru a suitable flue pipe 28 which prefere ly extends upwardly within the tank 10. For example this luc has been shown as connected to the lowe-r portion of heat transferring pipe 21, as by means of the short pipe section 29, and has its upper end projecting thru the tank 10. The flue 28 is preferably spaced from the inner walls ot' tank l0 but is oliset from the center of the same for a purpose later to be explained. To provide sufliclent space for this flue between pipe 21 and the side of tank 10, pipe 2l may be slightly ott'set from the center of the tank as shown.

ln operating the heater described above, llame from theburner '1l is projected into the tire tube 25 and strikes the upper end of heat exchange tube 21. By reason of the drat't produced by flue 28, the products of combustion are then caused to move downwardly thru the passageway provided between tubes 23 and 2l and are then drawn upwardly thru tine 28. lleat is imparted to the liquid in the tank both by the tube 2l and by the flue 28. Since the flue 28 extends upwardly along one side ot' the tank a thermal circulation ot' the liquid is established somewhat as indicated by the arrows in the drawing. A part of thc cooler liquid tiowing downwardly along the thc left portion of the tank as shown in the drawing, will be diverted u wardly as it nears the upper portion of tu e 21 and will then flow u wardly in warming currents along the ue 28. Other cooler currents however will flow downwardly to the lower portion of the tank and then upwardly along the lower portion of flue 28 as shown. When all the water in the tank is cold and the heater is initiated in to operation, the thermal circulation will not cause hot water to be stored in a layer at the top of the tank, but will maintain a positive circulation and cause a substantially equal rise in ten'iperature of the water throughout all portions of the tank. 'lhis mode ot operation `ditterentiates my liquid heater l'rom others in which the thernml circulation lnerely serves to deposit hot water at the top ot' the tank to displace the colder water. I have tound that water heaters operate more etliciently as a whole when the circulation is sutl'icient to cause a general movement of water throughout the tank, and in this invention such a circulation is effected by the use of a large heat exchange surface which insures efficient transfer of heat from the products of combustion.

lVhen the tank has been heated to a temperature of say in thc neighborhood of 1509 F., only a few degrees of temperature difference exists between tbe top and bottom of the tank. In practice the tla'me from the continuous pilot burner 16 is sufficient to maintain the liquidin this heated condition providing no hot water is withdrawn. However as soon as water is withdrawn thru pipe 12, cold water entering thru pipe l1 actuates the automatic valve 18 to supply gas to the mam burner 14, which then heats the additional cold liquid until the temperature ot the entire tan t has again reached a certain maximum value depending upon the setting of valve 18. lVhen the tank is filled with cold water and the burner is ignited, a small amount of condensation occurs which may bc drained from the pipe 21 and flue 28, as by meansl ot a small drain pipe 31.

The high thermal etliciency of this heater is also due in 'part to the fact that the products ot' combustion move at a relatively low velocity. because their direction of travel is reversed both when entering the heat exehangetube 21 and when entering the flue 28. Furthermore since the flue 28 is entirely within the tank, all of the heat given up by the products of combustion must be imparted to the liquid of the tank. except that which remains in the discharged flue gases.

I claim:

l. In a liquid heater for hot water supply systen'is, an upright liquid tank` a source of cold water in communication with the lower portion of the tank, a pipe conm'lunicating with the upper portion of thc tank for withdrawing hot water, a heat exchange tube extending upwardly into said tank from the bottom thereof, a lire tube of smaller diameter than the heat exchange tube and extending upwardly in the heat exchange tube, said lire tube being spaced l'rom the upper end of the heat exchange tube, a fuel burner adapted to project a flame into said fire tube, and a single upright flue disposed within and extending substantially the length of the tank. said flue communicating with the atmosphere at its upper end, and with the lower portion of said heat exchange tube at its lower end.

2. In a liquid heater for hot water supply systems, an upright liquid tank, a source of cold water in communication with the lower portion of the tank, a pipe communieating with the upper portion ofthe tank l'or witlnlrawing hot water, a single heat exchange pipe extending upwardly into tln` tank from the lower end thereof, a fuel burner coopcrably associated with the lower portion of said pipe. a passage for conveying and discharging products of combustion into the upper portion ot' said heat exchange pipe, a single flue pipe extending upwardly thru said tank for substantially the entire length thereof, the lower end of said flue pipe extending down beside said heat cxcliangc pipe, and a pipe connection within the tank establishing communication between the lower portion of said heat exchange pipe and said flue pipe, whereby products of combustion are caused to travel downwardly thru the heat exchange pipe and upwardly thru the flue pipe.

3. In a liquid heater for hot water supply systems, an upright liquid tank, a source of cold water in communication with the lower portion of the tank, a pipe communicating with the upper portion of the tank for withdrawing hot water, a single heat exchange pipe extending upwardly into the tank from the lower end thereof, the upper end of said pipe being closed and terminating medially of the tank, a burner associated with the lower portion of said pipe, a fire tube extending upwardly into said pipe and being of a smaller diameter than said pipe, said tube serving to convey products of combustion upwardly into the pipe and to discharge the same adjacent the upper end of the same, a flue pipe extending substantially the entire length of the tank, said flue pipe being within the tank and offset from the center of the tank along only one side thereof, and a pipe connection within the tank between the lower portion of said heat exchange pipe and said flue pipe, said arrangement of pipes causing products of combustion to flow downwardly thru the heat exchange pipe and upwardly thru the Hue pipe, the Ioffset positioning of the flue pipe serving to aid in establishing a thermal circulation of water within the tank.

4. In a liquid heater' for hot water supply systems, a liquid tank, a source of cold water supply in communication with said tank, a

pipe for withdrawing hot water, a fuel burner, a lire tube in communication with said burner and extending into said tank, a heat exchange pipe extending about said tire tube in a spaced relationship thereto, said lire tube serving to carry products of combustion received from said burner upwardly into said heat exchange tube, and a iue ex tending thru said tank and in communication with a lower portion of said heat exchange tube.

In testimony whereof, I have hereunto set my hand.

THOMAS G.- ARRUWSMUFH. 

